What size water heater for a family of 4?46 gal first-hour rating
Size the busiest hour, then compare first-hour ratings on the EnergyGuide label.
Your starting point
46 gal first-hour rating
Compare first-hour ratings, not tank volume.
Planning range
44–48 gal FHR
A screening estimate under the assumptions below. The range is a shopping guide, not a guarantee.
Planning estimate. A licensed contractor must confirm the final size, installation and local code requirements. Electrical work needs a licensed electrician.
Adjust your home
The calculation, step by step.
Peak-hour events x DOE worksheet hot-water gallons; compare with first-hour rating, not tank volume.
| Input or step | Calculated amount |
|---|---|
| Shower x 4 | 40 gallons |
| Shave x 1 | 2 gallons |
| Hand dishes x 1 | 4 gallons |
| Dishwasher x 0 | 0 gallons |
| Washer x 0 | 0 gallons |
What moves this number?
Peak-hour showers
Each worksheet shower adds 10 gallons of hot water.
Appliances
A dishwasher adds 6 gallons; a clothes washer adds 7.
Recovery rate
Two tanks of the same volume can have different first-hour ratings.
Your location and assumptions.
Location does not change this model. The selected appliance loads, room conditions or peak usage determine the result.
- Household default assumes one shower per person in the same hour, one shave and one hand-dishwashing event.
- Illustrative tank shopping band: 40-60 gallons. This is a household heuristic, not an FHR conversion.
- Measure unusual baths and check actual appliance hot-water use.
What might it cost to run?
Capacity alone does not establish monthly cost. Compare each model’s EnergyGuide annual consumption at your tariff, and account for operating mode, inlet temperature and actual hot-water use.
Before you choose equipment.
Final selection must deliver at least your measured peak demand at the operating mode and winter inlet temperature. A nominal tank size alone is insufficient.
Bring this calculation to your installer. They will check the measured load, manufacturer performance, distribution or connections, installation conditions and local requirements.
A few more sizing questions.
What size water heater for a family of 4?
The default screen gives 46 gal first-hour rating, with a planning range of 44–48 gal FHR. Change the inputs above to reflect your actual home. The illustrative tank shopping band is 40–60 gallons, but first-hour rating is the sizing check.
Is first-hour rating the same as tank volume?
No. First-hour rating includes stored water and recovery during the hour. Two tanks with the same volume can deliver different amounts. Compare the label at the intended operating mode.
How many showers should I enter?
Enter shower events during the single busiest hour, even if they happen sequentially. The worksheet uses 10 gallons of hot water per event; measure longer showers and large baths separately.
Does a heat-pump water heater need a different size?
Its first-hour rating depends on operating mode and conditions. Verify the model rating and any backup-resistance use rather than converting household count directly into tank volume.
Should every appliance be counted?
Count only the hot-water uses in that busiest hour. The worksheet assumes 6 gallons per dishwasher cycle and 7 per clothes-washer load; actual efficient appliances may differ.
Is this a final equipment size?
No. A licensed contractor must measure your building or actual loads, check manufacturer performance and local code, and confirm the final selection.